1. Field of the Invention
The present invention relates to improvements of an image inspection method and an image inspection device for inspecting an inspection object for a defect from an image by taking an image of a plate-shaped inspection object having a property of transmitting infrared rays, for example, like a semiconductor wafer, using infrared rays.
2. Description of the Related Art
There is a device that inspects a plate-shaped transparent or translucent inspection object, such as a semiconductor wafer and a liquid crystal panel, for a defect (crack or adhesion of foreign matter) using light. Herein, for ease of description, a case where the inspection object is a semiconductor wafer will be described. It should be appreciated, however, that application of the invention is not limited to a semiconductor wafer (occasionally, referred to also as a cell). For example, JP-A-8-220008 discloses an inspection device that detects a crack of a semiconductor wafer as an inspection object by irradiating infrared rays to the semiconductor wafer. In FIG. 1 of JP-A-8-220008 are shown an inspection object 1 that transmits infrared rays, a fine adjustment stand 2 that holds the inspection object 1, an infrared light source 10 that irradiates infrared rays 12 to the inspection object 1, a diffuser 11 provided in close adhesion to the infrared light source 10, and infrared rays 12 coming out from the diffuser 11. Infrared rays 32 having passed through the inspection object 1 are detected by an infrared camera 15 equipped with an infrared lens 14, and displayed in the form of an image on a monitor 16 into which a video signal from the infrared camera is inputted.
Operations of the inspection device disclosed in JP-A-8-220008 will now be described. Infrared rays emitted from the infrared light source 10 are made homogeneous by the diffuser 11 and irradiate the inspection object 1 from the back surface thereof. In this instance, the inspection object 1 is held by the fine adjustment stand 2 at the both ends (from the lower side). Irradiated infrared rays come out from the main surface of the inspection object 1, and these transmitted infrared rays are captured into the infrared camera 15 by means of the infrared lens 14. The monitor 16 then displays an output image from the infrared camera in the form of a video that can be confirmed visually. Assume that the inspection object 1 is a semiconductor wafer before processing, for example, patterning processing, is applied thereto, then, because a transmission state of infrared rays differs between a crack and the other portions, the crack can be readily detected.
The inspection device disclosed in JP-A-8-220008 inspects the inspection object 1 using transmitted infrared rays that have passed through the inspection object 1 from the back surface to the main surface. However, because light is blocked by the fine adjustment stand 2 at the peripheral portion of the cell, light is not allowed to pass through this portion, which poses a problem that an inspection cannot be conducted in this portion. Whereas a defect of a semiconductor wafer is more likely to occur in the peripheral portion, and there has been a need to inspect the peripheral portion of a semiconductor wafer as well in order to enhance the yield of semiconductor wafers.
As has been described, the image inspection method and the image inspection device in the related art are configured in such a manner that the peripheral portion of an inspection object is shielded by a device holding the inspection object. Hence, when configured to conduct an inspection using transmitted light, light is not allowed to pass through the shielded portion. This raises a problem that there is a portion where an inspection cannot be conducted. It is, however, desirable to inspect the periphery of an inspection object, which is not necessarily limited to a semiconductor wafer, in order to fully utilize the inspection object to the periphery.